1. Field of the Invention
The present invention relates to an apparatus and method for automatically adjusting tilting of an optical disc drive, and more particularly, to an apparatus and method for automatically adjusting tilting of an optical disc drive using an autocollimator.
2. Description of the Related Art
Optical disc drives generally write and read data on and from an optical disc using a beam emitted from an optical pickup unit, that slides in a radial direction of the optical disc.
FIG. 1 is a perspective view of a general optical disc drive. Referring to FIG. 1, a spindle motor 20 and a pair of rails 30 are installed on a main base 10. An optical pickup unit 40 is installed to be capable of sliding along the rails 30.
The spindle motor 20 spins an optical disc D, and a turntable 50 on which the optical disc D is placed is combined with a shaft of the spindle motor 20. The optical pickup unit 40 writes and reads data on and from a recording surface of the optical disc D, and slides along the rails 30 in a radial direction of the optical disc D.
To accurately read and write data on and from the recording surface of the optical disc D, the recording surface of the optical disc D has to be at a predetermined angle with respect to an optical axis of a beam emitted from the optical pickup unit 40. To accomplish this, the surface of the turntable 50 has to be parallel with the rails 30 that guide the sliding of the optical pickup unit 40.
In general, the surface of the turntable 50 fails to be parallel with the rails 30 due to errors in manufacturing parts of the spindle motor 20 and the rails 30, and errors occurring when assembling the parts. Thus, deviation of an angle formed by the optical axis of the beam emitted from the optical pickup unit 40 and the recording surface of the optical disc D, from a predetermined angle, is called tilting. Tilting has two components: radial tilting, Tr, that refers to the slope in a direction where the optical pickup unit 40 slides along the surface of the optical disc D, i.e., in the radial direction of the optical disc D; and tangential tilting, Tt, that refers to the slope in a direction perpendicular to the radial direction.
Referring to FIG. 1, a tilting adjusting method includes adjusting the slope of the spindle motor 20 and adjusting the slope of the rails 30. Methods of adjusting the slope of the rails 30 are classified into a two-point adjusting method, by which two parts, P3 and P4, around the outer circumference of the optical disc D are adjusted, and a three-point adjusting method, by which two parts P3 and P4, and part P2 are adjusted. If the three-point adjusting method is used, P1 is a fixed part. Since the two-point adjusting method degrades the accuracy of adjusting tangential tilting, the three-point adjusting method is primarily used.
A process of adjusting tilting using the three-point adjusting method will be described. First, a degree of parallelism between the turntable 50 and the rails 30 is measured using optical equipment to calculate the amount of tilting. Next, a worker adjusts the rails 30 at the three adjusting parts P2, P3, and P4, according to the amount of tilting. Here, the worker repeats the adjusting until the amount of tilting is within a predetermined permitted limit.
When manufacturing optical disc drives, a process of adjusting tilting is generally performed. In a case where errors occur frequently when adjusting tilting, it takes a considerable amount of time to adjust tilting. Thus, the efficiency of production of optical disc drives decreases. Also, since a worker adjusts the rails to adjust tilting, when an unskilled worker adjusts tilting, the uniformity of adjusting tilting generally decreases, and a significant amount of time is required for adjusting tilting.